In principle they are the same, the OVA is just another way of packaging the files.
From the VMware documentation "OVF is a file format that supports exchange of virtual appliances across products and platforms. OVA is a single file distribution of the same file package."

A single file OVA is a tar package of the OVF files.

I personally find a single OVA file easier to distribute and store.
A potential drawback could be the extra extraction step you need with an OVA file.